The Post's Lenny Bernstein explains a new report that shows life expectancy for Americans has declined for the first time since 1993. (Monica Akhtar,Gillian Brockell/The Washington Post)

For the first time in more than two decades, life expectancy for Americans declined last year — a troubling development linked to a panoply of worsening health problems in the United States.

Rising fatalities from heart disease and stroke, diabetes, drug overdoses, accidents and other conditions caused the lower life expectancy revealed in a report released Thursday by the National Center for Health Statistics. In all, death rates rose for eight of the top 10 leading causes of death.

Life expectancy at selected ages, by sex (CDC/NCHS/HHS/NVSS)

“I think we should be very concerned,” said Princeton economist Anne Case, who called for thorough research on the increase in deaths from heart disease, the No. 1 killer in the United States. “This is singular. This doesn’t happen.”

A year ago, research by Case and Angus Deaton, also an economist at Princeton, brought worldwide attention to the unexpected jump in mortality rates among white middle-aged Americans. That trend was blamed on what are sometimes called diseases of despair: overdoses, alcoholism and suicide. The new report raises the possibility that major illnesses may be eroding prospects for an even wider group of Americans.

Its findings show increases in “virtually every cause of death. It’s all ages,” said David Weir, director of the health and retirement study at the Institute for Social Research at the University of Michigan. Over the past five years, he noted, improvements in death rates were among the smallest of the past four decades. “There’s this just across-the-board [phenomenon] of not doing very well in the United States.”

Overall, life expectancy fell by one-tenth of a year, from 78.9 in 2014 to 78.8 in 2015, according to the latest data. The last time U.S. life expectancy at birth declined was in 1993, when it dropped from 75.6 to 75.4, according to World Bank data.

The overall death rate rose 1.2 percent in 2015, its first uptick since 1999. More than 2.7 million people died, about 45 percent of them from heart disease or cancer.

Age-adjusted death rates for the 10 leading causes of death. (CDC/NCHS/HHS/NVSS)

Experts cautioned against interpreting too much from a single year of data; the numbers could reverse themselves next year, they said.

“This is unusual, and we don’t know what happened,” said Jiaquan Xu, an epidemiologist and lead author of the study. “So many leading causes of death increased.”

The report’s lone bright spot was a drop in the death rate from cancer, probably because fewer people are smoking, the disease is being detected earlier and new treatments have been developed recently, experts said.

The largest rate jump for any cause of death was for Alzheimer’s disease, which went from 25.4 to 29.4 deaths per 100,000 people. But several experts attributed that to greater reporting of the disease as a cause of death, not by any huge growth in the number of people who died.

Death rates rose for white men, white women and black men. They stayed essentially even for black women and Hispanic men and women. “It’s just confirming this deterioration in survival for certain groups,” said Ellen Meara, a professor at the Dartmouth Institute for Health Policy and Clinical Practice. She wonders what factors might be protecting Hispanic men and women from the negative trend.

According to the new report, males could expect to live 76.3 years at birth last year, down from 76.5 in 2014. Females could expect to live to 81.2 years, down from 81.3 the previous year.

Life expectancy at age 65 did not fall, another indication that the diseases behind the lower life expectancy occur in middle age or younger. At 65, men can expect to live 18 more years, while women survive an average of 20.6 more years, the data shows. Infant mortality rose slightly, according to the report, but the difference was not considered statistically significant.

Heart disease was responsible for more than 633,000 deaths in 2015, up from a little more than 614,000 the previous year. Cancer killed more than 595,000 people.

“We’re seeing the ramifications of the increase in obesity,” said Tom Frieden, director of the Centers for Disease Control and Prevention. “And we’re seeing that in an increase in heart disease.”

The number of unintentional injuries — which include overdoses from drugs, alcohol and other chemicals, as well as motor vehicle crashes and other accidents — climbed to more than 146,000 in 2015 from slightly more than 136,000 in 2014. Public health authorities have been grappling with an epidemic of overdoses from prescription narcotics, heroin and fentanyl in recent years. Xu said overdose statistics were not yet ready to be released to the public.

Deaths from suicide, the 10th-leading cause of death in the United States, rose to 44,193 from 42,773 in 2014.

Several experts pointed out that other Western nations are not seeing similar rises in mortality, suggesting an urgency to determine what is unique about health, health care and socioeconomic conditions in the United States.

“Mortality rates in middle age have totally flat­lined in the U.S. for people in their 30s and 40s and 50s, or have been increasing,” Case said. “What we really need to do is find out why we have stopped making progress against heart disease. And I don’t have the answer to that.”

Meara noted that more people need better health care but that “the health-care system is only a part of health.” Income inequality, nutrition differences and lingering unemployment all need to be addressed, she said.